1. Field of the Invention
The present invention relates to a magnetic recording medium having recording elements formed as convex portions and a filling material filled within the concave portions between the recording elements and a magnetic recording/reproducing device including the medium.
2. Description of the Related Art
The areal densities of conventional magnetic recording media such as a hard disk have come to be greatly increased with improvements such as miniaturization of magnetic grains forming the recording layers, modification of materials, or highly precise processing of the head. Even more improvements in the areal density are expected in the future. However, the limit of head processing, erroneous recording of information in a track adjacent to a target track caused by the broadening of a magnetic field and cross talk have been encountered, and improvements by the conventional techniques have reached the limit.
In the meantime, a discrete track medium or a patterned medium has been proposed as a candidate medium enabling the realization of further improvement of the areal density. These media have a recording layer formed in a predetermined concavo-convex pattern in which recording elements are formed as convex portions.
On the other hand, if there is large difference in the level between the concavities and convexities on the surface of a magnetic recording medium such as a hard disk, the flying height of the head slider becomes unstable, and good recording/reproducing characteristics cannot be obtained. Therefore, in a proposed magnetic recording medium, the concave portions between the recording elements are filled with a filling material so that the surface of the recording layer is flattened (see, for example, Japanese Patent Laid-Open Publication No. 2000-195042).
Note that in order to prevent the recording layer from contacting the magnetic head, the recording layer is usually covered with a protective layer. A material having high hardness and good abrasion resistance is preferable as a material for such a protective layer, and a hard carbon film or the like is used. In order to reduce the magnetic gap between the magnetic head and the recording layer and obtain a good magnetic characteristic, the protective layer is preferably as thin as possible. Such a thin hard protective layer is liable to damages when it deforms, but the use of a less deformable material having high hardness and rigidity as a material for a part supporting the protective layer suppresses the deformation of the protective layer, which can suppress damages of the protective layer. In the discrete track medium or patterned medium, the filling material as well as the recording elements support the protective layer, and therefore it is preferable to use a rigid and hard material for the filling material. The filling material is preferably made of a hard material resistant to abrasion so that the abrasion of the surface of the magnetic recording medium for contact with the magnetic head be suppressed in the event that part of the protective layer peels. With no such protective layer, a magnetic recording medium may have its recording elements and filling material exposed at the surface. In the magnetic recording medium of this type, in particular, the filling material must have high rigidity and hardness.
Moreover, the filling material is preferably made of a material that is chemically stable and resistant to corrosion.
Various kinds of oxide, nitride, carbide or the like may satisfy the requirement for the filling material, and SiO2 (silicon dioxide) is known as a low cost material that can satisfy the requirement (see, for example, Japanese Patent Laid-Open Publication Nos. 2000-195042 and Hei 9-97419).
However, even the use of SiO2 as the filling material sometimes does not result in good recording/reproducing characteristics.